White grubs, the root-feeding larvae of scarab beetles (Coleoptera: Scarabaeidae), are important pests of turf and pasture grasses, ornamental plants, and numerous crops around the world. At least 10 species cause significant damage to turfgrasses in North America. In fact, a complex of primarily introduced white grub species are the major turfgrass insect pests. Among these, the Japanese beetle, Popillia japonica, has until recently been regarded as the key species, but other white grub species are becoming more important. These other species include the oriental beetle, Exomala orientalis, the European chafer, Rhizotrogus majalis, and the Asiatic garden beetle, Maladera castanea. Surveys have indicated that the oriental beetle has become the most important white grub species. The subterranean habit of the larvae of scarab beetles makes them some of the most difficult to control insect pests.
Chemical insecticides are the primary means of controlling white grubs. Organophosphate and carbamate insecticides are used for curative control of white grubs, however, toxicological and environmental problems related to their application have already or will soon lead to the loss of registrations of many compounds or uses of these compounds. The implementation of the Food Quality Protection Act of 1996 in the United States, for example, is responsible for these increasing restrictions on the use of organophosphates (and potentially also carbamates). While new types of insecticides with better toxicological and environmental characteristics (e.g., neonicotinoids, insect growth regulators) are becoming increasingly available for white grub control, these compounds generally have to be applied preventively because their efficacy declines with advancing white grub development. Because white grub outbreaks are generally difficult to predict, this preventive approach often results in the treatment of large areas that may only need partial or no treatment. This not only increases the cost of white grub management, but also may have unintended environmental consequences such as long-term suppression of beneficial insects.
Entomopathogenic nematodes (Heterorhabditidae and Steinernematidae) offer an environmentally safe ‘biopesticide’ alternative to chemical insecticides for the control of white grubs. These nematodes possess most of the characteristics of an ideal biological control agent for insects. Koppenhöfer, In: Lacey and Kaya (eds.), Field Manual of Techniques in Invertebrate Pathology, Kluwer Academic Publishers, pp. 283-301 (2000). Nematodes have been studied quite extensively as white grub control agents. However, overall the level of white grub control has been often inconsistent and unsatisfactory. Klein, In: Nematodes and the biological control of insect pests, CSIRO, East Melbourne, pp. 49-58 (1993). A reason for this inconsistency is the difference in nematode susceptibility among different white grub species. Thus, important white grub pests such as the European chafer or the oriental beetle, for example, are very resistant to infection by some of the previously used nematode species.